Low-Density Spin Susceptibility and Effective Mass of Mobile Electrons in Si Inversion Layers

Abstract

We studied the Shubnikov--de Haas (SdH) oscillations in high-mobility Si-MOS samples over a wide range of carrier densities $n\ensuremath{\simeq}(1--50)\ifmmode\times\else\texttimes\fi{}{10}^{11}{\mathrm{cm}}^{\ensuremath{-}2}$, which includes the vicinity of the apparent metal-insulator transition in two dimensions (2D MIT). Using a novel technique of measuring the SdH oscillations in superimposed and independently controlled parallel and perpendicular magnetic fields, we determined the spin susceptibility ${\ensuremath{\chi}}^{*}$, the effective mass ${m}^{*}$, and the ${g}^{*}$ factor for mobile electrons. These quantities increase gradually with decreasing density; near the 2D MIT, we observed enhancement of ${\ensuremath{\chi}}^{*}$ by a factor of $\ensuremath{\sim}4.7$.